Since the late 1950’s ultrasonography has become a very useful diagnostic tool in Obstetrics. The technology has advanced greatly in its half-century lifespan. Today’s equipment is able to provide real-time continuous pictures of the moving fetus. These images are created from high frequency sound waves emitted from a transducer that is placed in contact with the abdomen and moved around like a flashlight all around the uterus. Ultrasound beams can the fetus in thin slices and are reflected back on the transducer. The data obtained from different reflections are put back together as a picture on the monitor. This allows the physician to view malformations in the fetus, take measurements to assess gestational age, size and growth, and assess movements such as heart beat.
There can be some minor physical discomfort associated with an ultrasound. A full bladder is sometimes required for an ultrasound during early pregnancy. There can be some discomfort from pressure on the full bladder. The conducting gel may feel slightly cold and wet. There is no sensation at all from the ultrasound waves.
There is generally considered to be little danger in ultrasounds on pregnant women. There is no irradiation, unlike an x-ray. No harmful effects have been detected in the cells of experimental humans or animals in any of the large amount of studies that have so far been performed. Some smaller studies indicate apparent ill-effects such as low birthweight, but these have never been confirmed or substantiated in any larger studies. Most physicians today regard ultrasound as completely safe.
Over- and under- diagnosis brought about by inadequately trained staff, working in relative isolation or using poor equipment are the largest dangers of ultrasound. Any ultrasound diagnosis should be confirmed by a second physician, if at all possible.